Saving and Investing in Japan

Saving and investing in yen runs on the same arithmetic everywhere in the world — amounts, rates, time — wrapped in distinctly Japanese containers: insured deposits with a per-bank cap, a flat tax on interest and gains, and two generous tax-free wrappers whose 2024 reform reset the rules. This guide walks the ladder from ordinary deposit to NISA, with the mathematics each rung deserves.

Rung one: deposits, and the ¥10,000,000 question

The ordinary deposit (普通預金) holds transaction money; the time deposit (定期預金) locks a sum for a term at a fixed rate. Both are protected by the Deposit Insurance Corporation of Japan up to ¥10,000,000 of principal plus interest per depositor per bank — the number that decides when a saver becomes a bank-spreader. Within the cap, a deposit's risk is effectively zero; its return is whatever the product pays, which is why every calculator on this site makes the rate an input you type rather than a number we assert. The savings calculator projects the growth of deposits, contributions and compounding at exactly the rate your product publishes.

The tax on the second rung

Interest and, later, investment gains are generally subject to a flat withholding tax of about 20.315% — income tax, resident tax and the reconstruction surtax — outside tax-free wrappers. The practical consequence: a pre-tax projection overstates what you keep by about a fifth. Run the compound interest calculator at your product's rate, then discount the interest line by 20.315% for the after-tax truth. The exceptions — NISA and iDeCo — are the next rungs, and their value comes precisely from deleting that line.

NISA after the 2024 reform

The reformed NISA (from January 2024) is the main tax-free wrapper for Japanese retail investors:

• Annual purchases: up to ¥3,600,000 — ¥1,200,000 through the tsumitate (scheduled contribution) account and ¥2,400,000 through the growth (sōhatsu) account.
• Lifetime ceiling: ¥18,000,000 of purchases in total, of which growth-account purchases are capped at ¥12,000,000.
• Structure: the tsumitate account is designed for regular monthly investing; the growth account takes lump sums. Both shelter gains from the ~20.315% tax, indefinitely while held.

Verify current rules with your broker — ceilings and eligibility details are legislation, and legislation amends. The arithmetic point stands regardless: inside NISA, a 4% assumed return compounds untaxed; outside it, roughly a fifth of the growth is taxed away each realisation.

iDeCo: the deductible wrapper

iDeCo (個人型確定拠出年金) is the private-pension wrapper: contributions are tax-deductible, growth is tax-free, and the money invests toward drawdown from age 60 under plan rules — with December 2024 reforms making contribution amounts more flexible. It trades liquidity for deduction: the money is committed for decades, and the fees and plan options vary. For a saver whose marginal tax rate is meaningful, the deduction is the largest single subsidy Japanese personal finance offers; for one whose horizon may interrupt, it is a lock-up first.

The ladder, and inflation's vote

The conventional sequence holds up well in Japan: an emergency fund of several months' expenses in ordinary deposits; then regular investing through the tsumitate NISA at a pace you can sustain; then lump sums into the growth account, iDeCo or taxable accounts as income allows. The investment growth calculator projects any rung with an assumed return, a fee drag and an inflation view — the fee box matters because fees compound against you exactly as returns compound for you.

Inflation is the last vote, and Japan's history makes it non-obvious: through the deflation decades, yen saved quietly gained purchasing power; through recent inflation, they quietly lost it. A projection is nominal by design — what the statement will say — while the honest question is what the money will buy. If your assumed return sits near your expected inflation, the contribution column built your balance, not the interest column; know which one is doing the work. Start with the savings calculator, graduate to the investment growth calculator, and read how interest works to see the same mathematics running in reverse on every loan you carry.